As described in U.S. Patent Application Publication No. US 2012/0312569 by Redekop, in one known form of conservation tillage, the soil is minimally disturbed prior to planting in order to allow air to penetrate the mat of crop residue. This technique is variously known as minimum tillage, residue management, soil aeration or seedbed aeration. A farm implement, sometimes known as a vertical tillage implement, is used to cut the crop residue and penetrate a short distance into the surface of the soil while lifting the soil vertically to permit access of air to the soil.
A known construction of a vertical tillage implement comprises a main frame supporting a plurality of tillage units thereon in which each tillage unit comprises a disc supporting arm which is resiliently mounted relative to the main frame. A disc assembly is then mounted on the trailing end of the disc supporting arm in the form for a shaft and a hub which rotatably supports a ground engaging disc on the shaft.
During use of the vertical tillage implement, the soil is fractured in such a manner that a considerable amount of side flowing soil and residue movement results. Maintenance of prior art hub and shaft arrangements due to penetration of soil and residue into the bearing thereof is thus a known concern.